This invention relates to a novel method for filling or devacuating an evacuated electron tube with gas to atmospheric pressure. The invention relates particularly, but not exclusively, to a novel method for opening a cathode-ray tube to air at atmospheric pressure so that the tube may be regunned.
Some prior methods for opening a vacuum tube to air employ some technique for controllably cracking the neck or exhaust tubulation, as for example in U.S. Pat. Nos. 3,063,777 to A. M. Trax, 3,404,933 to R. J. Weideman, and 3,679,284 to E. S. Thall. In RCA Engineer, 15, 52-57 (1970), an article by D. Meyerhofer discloses how to open a cathode-ray tube to air by puncturing a small hole in a glass wall of the tube envelope with 15 long pulses of 3 joule energy of a laser beam. While each of these prior processes seeks to minimize the amount of loose particles generated by the process, nevertheless, loose glass particles are generated by the processes, which particles are swept into that portion of the tube which is to be salvaged and reused. Where the tube opening is achieved by cracking, the particles are largely generated when the glass is fractured. Where a laser beam punctures a hole in a glass wall by the prior method, particles are generated by fracturing and also when volatilized glass material is swept into the tube envelope and condenses therein.